PDZ domain found in a variety of Eumetazoan signaling molecules, often in tandem arrangements. May be responsible for specific protein-protein interactions, as most PDZ domains bind C-terminal polypeptides, and binding to internal (non-C-terminal) polypeptides and even to lipids has been demonstrated. In this subfamily of PDZ domains an N-terminal beta-strand forms the peptide-binding groove base, a circular permutation with respect to PDZ domains found in proteases.